This invention relates generally to melt spinning filaments or fibers using a spinnerette. More particularly, this invention relates to an apparatus for changing the number of filaments being spun from a single spinnerette.
Spinnerette assemblies for spinning synthetic filaments or fibers typically include an inlet block having an inlet port through which the material to be spun is introduced into the spinnerette assembly and a chamber containing filtering material, a distribution plate, a distribution cavity, a metering plate and a spinnerette plate. The metering plate includes a number of apertures having a compound shape, consisting of a capillary and a counterbore. The spinnerette plate normally includes a corresponding number of bores having a compound shape consisting of a counterbore or capillary and a jet or spinning orifice. U.S. Pat. No. 3,095,607 to Cobb describes a typical spinnerette assembly. Other spinnerette assemblies are described in U.S. Pat. No. 3,028,627 to McCormick, U.S. Pat. No. 2,883,261 to McGeorge, U.S. Pat. No. 3,225,383 to Cobb, U.S. Pat. No. 3,289,249 to Nakayama et al., U.S. Pat. No. 3,601,846 to Hudnall, U.S. Pat. No. 3,659,988 to Walczak, and U.S. Pat. No. 4,738,607 to Nakajima et al.
It is sometimes desirable to change the number of filaments being spun from a single spinnerette. Reasons for altering the filament count may include product variations, keeping the tow denier constant while changing the filament denier, changing quenching characteristics and maintaining spinning speed at higher denier per filament where extruder capacity is limited.
The traditional method for changing filament count is to individually plug spinnerette capillaries using a soft metal bar of approximately the same diameter as the counterbore. This method is time consuming, risks damage to the spinnerette and does not insure a leak-free seal.
Another known method for spinning a number of different filament counts from a single spinnerette plate is described in U.S. Pat. No. 3,336,633 to Curran. Curran employs metering plates having a number of apertures lower than the number of orifices in the spinnerette plate. Since the compound shape of the apertures in the metering plate are normally precision drilled to provide a desired pressure drop, the metering plates are relatively expensive to produce and maintaining a stockpile of metering plates to provide a variety of fiber counts may be cost-prohibitive.